<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div>Header</div>
  <div id="app">app</div>
  <div>Footer</div>

  <!-- 引用react -->
  <script src="https://unpkg.com/react@16/umd/react.development.js"></script>
  <script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
  <script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>

  <!-- 使用jsx -->
  <script type="text/babel">
    // 封装组件App
    class App  extends React.Component {
      constructor() {
        // 父类初始化
        super()
        // this.message = "Hello World"
        this.state = {
          message: "Hello World"
        }
      }
      render() {
        return (
          <div>
            <h2>{this.state.message}</h2>
            <button onClick={this.btnClick.bind(this)}>改变文本</button>
          </div>
        )
      }
      btnClick() {
        this.setState({
          message: "Hello React"
        })
      }
    }

    ReactDOM.render(<App/>, document.getElementById("app"))
  </script>
</body>
</html>
